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Subacute combined degeneration

Subacute combined degeneration of the spinal cord; SCD

 

Subacute combined degeneration is a disorder of the spine, brain, and nerves. It involves weakness , abnormal sensations , mental problems, and vision difficulties .

Causes

 

Subacute combined degeneration is caused by vitamin B12 deficiency. It mainly affects the spinal cord. But its effects on the brain and the peripheral (body) nerves are the reason for the term "combined." At first, the nerve covering (myelin sheath) is damaged. Later, the entire nerve cell is affected.

Doctors do not know exactly how a lack of vitamin B12 damages the nerves. It is possible that the lack of this vitamin causes abnormal fatty acids to form around cells and nerves.

People are at high risk for this condition if vitamin B12 cannot be absorbed from their intestine or if they have:

  • Pernicious anemia
  • Disorders of the small intestine, including Crohn disease
  • Problems absorbing nutrients, which can occur after gastrointestinal surgery

 

Symptoms

 

Symptoms include:

  • Abnormal sensations ( tingling and numbness )
  • Weakness of the legs, arms, or other areas

These symptoms slowly get worse and are usually felt on both sides of the body.

As the disease worsens, symptoms may include any of the following:

  • Clumsiness , stiff or awkward movements
  • Change in mental state , such as memory problems, irritability, apathy , confusion, or dementia
  • Decreased vision
  • Depression
  • Sleepiness
  • Unsteady gait and loss of balance

 

Exams and Tests

 

The health care provider will perform a physical exam. The exam usually shows muscle weakness and sensation problems on both sides of the body, especially in the legs. Knee jerk reflexes are often decreased. Muscles may develop spasticity . There may be reduced senses of touch, pain, and temperature.

Mental changes range from mild forgetfulness to severe dementia or psychosis . Severe dementia is uncommon, but in some cases, it is the first symptom of the disorder.

An eye exam may show damage to the optic nerve, a condition called optic neuritis . Signs of nerve inflammation may be seen during a retinal exam. There may also be abnormal pupil responses, decreased visual acuity , and other changes.

Blood tests that may be ordered include:

  • Complete blood count (CBC)
  • Vitamin B12 blood level
  • Methylmalonic acid blood level

 

Treatment

 

Early treatment improves the chance of a good outcome.

Vitamin B12 is given, usually by injection into a muscle. Injections are often given once a day for a week, then weekly for about 1 month, and then monthly. Vitamin B12 supplements, either by injection or high-dose pills, must continue throughout life to prevent symptoms from returning.

 

Outlook (Prognosis)

 

How well a person does depends on how long they had symptoms before receiving treatment. If treatment is received within a few weeks, complete recovery may be expected. If treatment is delayed for longer than 1 or 2 months, full recovery may not be possible.

Untreated, the disorder results in continued and irreversible damage to the nervous system.

 

Possible Complications

 

Complications can include permanent, progressive loss of nerve and mental functions.

 

When to Contact a Medical Professional

 

Call your health care provider if abnormal sensations, muscle weakness, or other symptoms of subacute combined degeneration develop. This is particularly important if you or a family member has had pernicious anemia or other risk factors.

 

Prevention

 

Some vegetarian diets, especially vegan, may be low in vitamin B12. Taking a supplement can prevent the disorder.

 

 

Open References

References

So YT, Simon RP. Deficiency diseases of the nervous system. In: Daroff RB, Fenichel GM, Jankovic J, Mazziotta JC, eds. Bradley's Neurology in Clinical Practice . 6th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 57.

 
  • Central nervous system

    Central nervous system - illustration

    The central nervous system is comprised of the brain and spinal cord. The peripheral nervous system includes all peripheral nerves.

    Central nervous system

    illustration

    • Central nervous system

      Central nervous system - illustration

      The central nervous system is comprised of the brain and spinal cord. The peripheral nervous system includes all peripheral nerves.

      Central nervous system

      illustration

    A Closer Look

     

      Self Care

       

        Tests for Subacute combined degeneration

         
           

          Review Date: 6/1/2015

          Reviewed By: Daniel Kantor, MD, Kantor Neurology, Coconut Creek, FL and Immediate Past President of the Florida Society of Neurology (FSN). Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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